Methods of and apparatuses for measuring electrical parameters of a plasma process

ABSTRACT

A sensor apparatus for measuring a plasma process parameter for processing a workpiece. The sensor apparatus includes a base, an information processor supported on or in the base, and at least one sensor supported on or in the base. The at least one sensor includes at least one sensing element configured for measuring an electrical property of a plasma and may include a transducer coupled to the at least one sensing element. The transducer can be configured to receive a signal from the sensing element and convert the signal into a second signal for input to the information processor.

CROSS-REFERENCE

The present application is a divisional application of U.S. patentapplication No. 13/159,266, filed Nov. 13, 2011, the entire contents ofwhich are incorporated herein by reference. U.S. patent application Ser.No. 13/159,266 is a divisional application of U.S. patent applicationSer. No. 11/281,238 filed Nov. 16, 2005, the entire contents of whichare incorporated herein by reference.

U.S. patent application Ser. No. 11/281,238 is a nonprovisional of U.S.Patent Application Ser. No. 60/722554, filed 30 Sep. 2005. The presentapplication likewise claims the priority benefit of U.S. PatentApplication Ser. No. 60/722554, filed 30 Sep. 2005.

The present application is related to U.S. Patent Application Ser. No.60/722554, filed 30 Sep. 2005; U.S. Pat. No. 6,691,068, filed 22 Aug.2000; U.S. Pat. No. 6,542,835, filed 22 Mar. 2001; U.S. PatentApplication 60/285439, filed 19 Apr. 2001; and U.S. Patent Application60/677545, filed 3 May 2005; all of these patents are incorporatedherein, in their entirety, by this reference.

TECHNICAL FIELD

This invention relates to methods of and apparatuses for measuringelectrical parameters within a plasma processing system. Morespecifically, this invention relates to plasma processes used to treatand/or modify the surfaces of work pieces such as semiconductor wafers,flat panel display substrates, and lithography masks.

BACKGROUND

Plasma processes are frequently used to modify or treat the surfaces ofworkpieces such as semiconductor wafers, flat-panel display substrates,and lithography masks. Conditions within a plasma process are designedto produce a complex mixture of ions, reactive chemical species (freeradicals), and energetic neutral species. The interaction of thesematerials then produces the desired effect on the surfaces of workpieces. For example, plasma processes are used to etch materials fromthe surfaces of semiconductor wafers so as to form complex electricalelements and circuits. The conditions within the plasma process arecarefully controlled to produce the desired etch directionality andselectivities.

The surface modifications produced by a specific plasma are sensitive toa number of basic parameters within the plasma. These parameters includesuch variables as: chemical concentrations (partial pressures),temperatures (both surface and gas phase), and electrical parameters(ion fluxes, ion energy distribution functions). A number of theseparameters (e.g. gas concentrations and pressure) can generally beeasily controlled using external actuators such as Mass Flow Controllers(MFCs) and servo driven throttle valves. Other important parameters(e.g. temperatures and free radical concentrations) can often beobserved or measured via sensor systems (e.g. thermocouples and OpticalEmission Spectrometers (OES)) installed on the process tool. A last setof important parameters such as ion fluxes and ion energies are moredifficult to either directly control or monitor.

A prime reason that these important electrical parameters are difficultto measure in a plasma process chamber is that the parameters resultfrom a complex, nonlinear interaction between the applied driving force(RF power) and the local physical state in the process chamber. Forexample, a localized increase in ion concentrations can lead to locallyincreased RF power flows, which in turn leads to higher ionconcentrations. This interaction and feedback can lead to highlynon-uniform and unstable plasma conditions. It is typically impossibleto adequately characterize the plasma state with a single, localizedmeasurement.

Plasma electrical parameters have been measured with a wide variety ofsensors and methods. These include: Biased probes (voltage or frequencyswept), Wall probes (swept frequency), Optical emission (actinometry andDoppler), Microwave absorption, and Passive electrodes (SPORT, CHARM).

Each of these sensor types and methodologies suffer from one of moresignificant flaws which prevent their routine use in plasma processmonitoring. Some of the most common flaws are that the sensors areeither unacceptably intrusive (they excessively modify or interact withthe local plasma state) or they provide an aggregate measurement lackingspatial resolution. Another deficiency found in some of the currentlyavailable techniques is their high cost due to the complexity andsensitivity of the instrumentation needed.

There is a need for improved methods and apparatuses for measuringplasma process parameters such those used for plasma processingsubstrates such as, but not limited to, semiconductor substrates, flatpanel display substrates, and lithography mask substrates. Moreparticularly, there is a need for improved methods and apparatuses formeasuring process parameters such as plasma density, plasma uniformity,ion energy distributions, electron energy distributions, ion fluxes, andion energies.

SUMMARY

This invention seeks to provide methods and apparatus that can overcomeone or more problems related to measuring electrical properties of aplasma for processing workpieces. One aspect of the present inventionincludes methods of measuring electrical properties of a plasma using asensor apparatus. The measurements include data for applications such asmonitoring, controlling, and optimizing processes and process tools.Another aspect of the present invention includes a sensor apparatus formeasuring electrical properties of a plasma for processing workpieces.

It is to be understood that the invention is not limited in itsapplication to the details of construction and to the arrangements ofthe components set forth in the following description or illustrated inthe drawings. The invention is capable of other embodiments and of beingpracticed and carried out in various ways. In addition, it is to beunderstood that the phraseology and terminology employed herein are forthe purpose of description and should not be regarded as limiting.

As such, those skilled in the art will appreciate that the conception,upon which this disclosure is based, may readily be utilized as a basisfor the designing of other structures, methods, and systems for carryingout aspects of the present invention. It is important, therefore, thatthe claims be regarded as including such equivalent constructionsinsofar as they do not depart from the spirit and scope of the presentinvention.

The above and still further features and advantages of the presentinvention will become apparent upon consideration of the followingdetailed descriptions of specific embodiments thereof, especially whentaken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a box diagram of a sensor apparatus according to an embodimentof the present invention and an external communicator.

FIG. 2 is a side view diagram of a sensor apparatus according to anembodiment of the present invention used in a plasma process chamber.

FIG. 3 is a top view diagram of an embodiment of the present invention.

FIG. 3A is a top view diagram of an embodiment of the present invention.

FIG. 4A is a side view of a sensing element according to one embodimentof the present invention.

FIG. 4B is an electrical schematic of the sensing element of FIG. 4A andan electrical schematic of a transducer according to one embodiment ofthe present invention.

FIG. 4C is a perspective view of a sensor apparatus according to oneembodiment of the present invention.

FIG. 5A is a side view of a sensing element according to one embodimentof the present invention.

FIG. 5B is an electrical schematic of the sensing element of FIG. 5A andan electrical schematic of a transducer according to one embodiment ofthe present invention.

FIG. 5C is a perspective view of a sensor apparatus according to oneembodiment of the present invention.

FIG. 6A is a side view of a sensing element according to one embodimentof the present invention.

FIG. 6B is a side view of a sensing element according to one embodimentof the present invention.

FIG. 7 is a diagram of one embodiment of the present invention.

FIG. 8 is a diagram of one embodiment of the present invention.

FIG. 9 is a diagram of one embodiment of the present invention.

Skilled artisans appreciate that elements in the figures are illustratedfor simplicity and clarity and have not necessarily been drawn to scale.For example, the dimensions of some of the elements in the figures maybe exaggerated relative to other elements to help to improveunderstanding of embodiments of the present invention.

DESCRIPTION

The present invention pertains to measuring process parameters forprocessing a workpiece using a plasma process. The operation ofembodiments of the present invention will be discussed below, primarily,in the context of processing semiconductor wafers, lithography masksubstrates, or flat panel display substrates. However, it is to beunderstood that embodiments in accordance with the present invention maybe used for measuring plasma process characteristics for essentially anyplasma-processing step involving a workpiece subjected to possibletemporal and/or spatial variations in plasma process conditions and/orprocess conditions that occur during plasma processing.

In the following description of the figures, identical referencenumerals have been used when designating substantially identicalelements or steps that are common to the figures.

Reference is now made to FIG. 1 wherein there is shown a block diagramfor a sensor apparatus 100 according to one embodiment of the presentinvention. Sensor apparatus 100 is configured for measuring a processparameter for plasma processing a workpiece. Sensor apparatus 100 isfurther configured for transmitting or receiving information. Forillustration purposes, FIG. 1 also shows an external communicator 160which may be used for communication with embodiments of the presentinvention.

Sensor apparatus 100 includes a base 115, a sensor 120, preferably aplurality of sensors 120, an information processor 130, an internalcommunicator 140, and a power source 150. Sensors 120, informationprocessor 130, internal communicator 140, and power source 150 aresupported on or in base 115. Sensors 120 are connected with informationprocessor 130 so as to allow signals generated by sensors 120 to beprovided as input to information processor 130. Information processor130 is connected with internal communicator 140 so as to allowinformation and data from information processor 130 to be transferred tointernal communicator 140. In preferred embodiments, informationprocessor 130 is connected with internal communicator 140 so as to allowbi-directional information transfer between information processor 130and internal communicator 140.

Sensors 120 may include discrete sensor devices attached to base 115.Alternatively, sensors 120 may be fabricated as part of base 115. Inother words, base 115 may be processed to fabricate sensors 120 as anintegrated part of base 115. Sensors 120 are designed to provide anelectrical signal proportional to one or more plasma process parametersrepresentative of the plasma process and process tool. Examples ofprocess parameters of importance for applications such as semiconductorprocessing and flatpanel display processing include radio frequency (RF)field, plasma potential, ion flux, electromagnetic flux such as light,and any process parameter that is affected by the plasma used for theprocess. Examples of typical sensor types include: defined area probesfor measuring plasma potential and measuring ion flux; Van der Pauwcrosses for measuring etch rate; isolated field transistors formeasuring plasma potential; and current loops for measuring ion flux andmeasuring RF field. The numbers and types of sensors are selected basedupon the specific application and process requirements.

In preferred embodiments of the present invention, sensor 120 comprisesa sensing element 120A and a transducer 120B. Sensing element 120A isconfigured so as to be responsive to the process parameter beingmeasured so that sensing element 120A produces a signal proportional toa plasma process parameter, such as a signal proportional to themagnitude of the process parameter. Transducer 120B is connected withsensing element 120A to receive the signal from sensing element 120A.Transducer 120B converts the signal from sensing element 120A into asignal for which information processor 130 is configured to receive.

In more preferred embodiments of the present invention, sensing element120A and transducer 120B are configured so as to provide improvedoperation of the sensor. The sensing element is configured to moreeffectively accommodate the process parameter being measured and thetransducer is configured so as to convert the signal from the sensingelement to accommodate the signal measurement requirements for theinformation processor. For some embodiments of the present invention,sensor apparatus 100 is configured for substantially non-intrusivemeasurement of important plasma parameters used for processingworkpieces. For such embodiments, sensor 120 is configured so thatsensing element 120A does not require direct electrical connections tothe plasma.

For some applications for embodiments of the present invention, it isnecessary or desirable to convert the output of the sensing element intoa form that is more easily or more accurately measurable. As an example,the output of a particular sensor type (e.g. capacitive current) may bean alternating RF voltage while the measurement circuitry is optimizedfor measuring a DC voltage. In these cases, one embodiment of thepresent invention includes a transducer used to transform the raw outputof a sensing element into a more readily measured form that can beaccommodated by the information processor. For some embodiments of thepresent invention, the transducer can also be used to scale the sensoroutput into a suitable measurement range. The selection of anappropriate transducer circuit is dependent upon both the sensingelement being used as well as the measurement circuitry. In someembodiments of the present invention, the transducer circuit can beintegrated into the sensor. For some embodiments of the presentinvention, the sensing element and the transduction method andcomponents are treated as independent elements that are optimized for aparticular process parameter measurement.

In one embodiment of the present invention, sensor apparatus 100includes a plurality of sensors 120 configured for measuring RF currentor RF voltage; an example of a suitable sensor is a capacitive sensor.More specifically, sensors 120 include sensing elements 120A comprisingcapacitive elements. For this embodiment, sensors 120 are configured aspart of sensor apparatus 100 so as to be in series with radio frequencycurrent flow from the plasma, through the plasma sheath, and into base115. The capacitive element is designed to have a low relative reactanceso as to produce a minimal perturbation of the plasma. Morespecifically, preferred embodiments of a capacitive sensor areconfigured so as to minimize a local increased impedance for the plasma.As an option for another embodiment of the present invention, sensorapparatus 100 includes one or more differential capacitive sensorsformed by coupling two adjacent capacitive elements so as to extrapolatelocal radio frequency voltages.

In another embodiment of the present invention, sensor apparatus 100includes a plurality of sensors 120 configured for measuring RFcurrents; an example of a suitable sensor is an inductive sensor. Morespecifically, sensors 120 include sensing elements 120A comprising aninductor coil such as a closed loop of magnetically permeable materialand a second electrically conductive coil wrapped around themagnetically permeable loop in a toroidal fashion as a sense coil. Inother words, one embodiment of the present invention includes a toroidalcoil with a magnetically permeable material core. The loop ofmagnetically permeable material is orientated substantially parallel tothe surface of base 115 such that radio frequency current from theplasma passes through the loop. The radio frequency current induces analternating magnetic field within the closed loop of magneticallypermeable material. The alternating magnetic field induces a currentflow within the sense coil. The current in the second electricallyconductive loop is applied to transducer 120B.

In another embodiment of the present invention, sensor apparatus 100includes a plurality of sensors 120 configured for measuringelectrostatic charge; in other words, electrostatic charge sensors. Morespecifically, sensors 120 include sensing elements 120A responsive toelectrostatic charge. In one configuration, sensing elements 120Aincludes a layer of an electrical conductor such as a layer of metal anda semiconductor such as a semiconductor layer. The electrical conductoris proximate to the surface of the semiconductor and electricallyisolated from the semiconductor. As an option for one embodiment, theelectrical conductor and the semiconductor are separated by a layer ofan electrically insulating material. In this configuration, chargecollected on the electrical conductor can moderate the conductivity ofthe semiconductor. Transducer 120B is configured so as to measure theconductivity of the semiconductor. In operation, charge is collected onthe electrical conductor as a result of exposure to the plasma for whichprocess parameters are being measured. The conductivity of thesemiconductor is measured in order to determine the magnitude of thecharge collected. As an option for some embodiments of the presentinvention, differential measurements can be made for semiconductinglayers having different thicknesses of dielectric between the electricalconductor and the semiconductor so as to produce an estimation of thecharge and potential.

In still another embodiment of the present invention, sensor apparatus100 includes a plurality of sensors 120 configured for measuring opticalemission from the plasma; in other words, optical emission sensors. Morespecifically, sensors 120 include sensing elements 120A responsive tooptical emission intensity. Sensing elements 120A include photosensitivematerial that undergoes a change in resistance in response to opticalemissions from the plasma. The changes in the resistance are correlatedto plasma properties such as local plasma densities and local iondensity. As an option for some embodiments of the present invention,sensing elements 120A further include an optical filter for filteringlight from the plasma so as to selectively permit or inhibit variouswavelengths of interest. Optionally, the properties of thephotosensitive material may be selected so that the wavelength responseof the photosensitive material extends beyond the visible spectrum.

Preferred embodiments of the present invention use one or more of thefollowing transducer circuits in transducer 120B at or near each sensorposition on sensor apparatus 100: diode rectification, power detection,optical transduction, and resistance measurement. For the dioderectification circuit, radio frequency voltages or radio frequencycurrent induced in a capacitive or inductive sensing element, asdisclosed above, are connected through a diode to a high impedance load,such as a high resistance load, to provide a measure of the peak to peakradio frequency potential. Alternatively, the radio frequency voltagesor radio frequency current induced in a capacitive or an inductivesensing element is connected to a low impedance load to provide ameasure of the local radio frequency current. In a further embodiment,identical sensor elements are connected to impedances of differentvalues so as to be capable of measuring nonlinear plasma current-voltagecharacteristics. As an option for another embodiment of the presentinvention, signals from the sensing elements may be applied to a complexload having resistive, inductive, and capacitive properties so as to becapable of making frequency sensitive measurements.

For the power detection circuit, transducer 120B includes a resistor anda temperature measuring device coupled so that the temperature measuringdevice, such as a thermistor, measures the temperature of the resistor.Radio frequency current (either RF or direct current) induced in sensingelement 120A is coupled to the resistor. The currents cause heating ofthe resistor as determined by the product of the current squaredmultiplied by the resistance of the resistor. The temperature rise ofthe resistive element is then detected using the temperature measuringdevice. Preferably, the temperature measuring device is electricallyisolated from the resistor.

Embodiments of the present invention for which transducer 120B comprisesan optical transduction circuit, the transduction circuit preferablyincludes a light emitting diode. The light emitting diode is connectedwith sensing element 120A so as to receive current signals from sensingelement 120A. The intensity of the light emitted by the light emittingdiode is proportional to the current received by the light emittingdiode. Transducer 120B further includes a light detecting device such asa photoresistor or a photodiode. The light detecting device is arrangedso as to be capable of measuring light produced by the light emittingdiode so as to produce a current proportional to the light produced bythe light emitting diode. The current from the light measuring device isapplied to the information processor as described above.

In some embodiments of the present invention that use sensing elements120A configured to provide an impedance proportional to the propertybeing measured, transducer 120B is incorporated in an impedancemeasuring circuit. In a preferred embodiment for measurements on a largenumber of sensors, transducer 120B is configured as a node in acrosspoint network substantially as described in commonly owned U.S.Pat. No. 6,542,835 and U.S. Pat. No. 6,789,034. The contents of U.S.Pat. No. 6,542,835 and U.S. Pat. No. 6,789,034 are incorporated hereinin their entirety by this reference.

In a preferred embodiment of the present invention, sensing element 120Aproduces an output signal such as current, voltage, and RF current. Theoutput signal from sensing element 120A is coupled to a transducer 120Bwhere the output signal from sensing element 120A is converted to achange in electrical resistance proportional to the process parameterthat is being measured. Transducer 120B is incorporated as a node in acrosspoint network of resistors. Changes in the resistance produced bytransducer 120B are measured with the crosspoint network of resistors asdescribed in commonly owned U.S. Pat. No. 6,542,835 and U.S. Pat. No.6,789,034. In a more preferred embodiment, the crosspoint networkincludes reference resistors of known value. Details of such acrosspoint network are provided in commonly owned U.S. Pat. No.6,542,835 and U.S. Pat. No. 6,789,034.

The electrical output of sensors 120 may be applied to informationprocessor 130 and digitized therein in a number of ways. In oneembodiment of the present invention, the electrical output from sensors120 comprises direct voltage. Sensor apparatus 100 includes analogmultiplexers used to allow data acquisition from a large number ofsensors 120 distributed on the surface of base 115. Electrical currentflows may be measured by monitoring the voltage developed across a knownresistance. In another embodiment, sensor apparatus 100 includes adiscrete ND circuit either integrated into or located in close proximityto sensors 120. In such an embodiment, the measured parameter istransmitted in digital form to electronics module 130.

For sensors which produce a change in capacitance in response to theparameter being measured, the measurements may be obtained bydetermining the time required to transition between two establishedvoltage states as a result of charging from a known current source orimpedance. Alternatively, a capacitive divider circuit formed using aknown capacitance may be driven with an alternating voltage of knownmagnitude and the magnitude of the divided signal used to derive thesensor measurement value.

Power source 150 is connected with information processor 130 so as toprovide electric power to information processor 130. Power source 150 isconnected with internal communicator 140 so as to provide electric powerto internal communicator 140. Embodiments of the present invention mayinclude sensors 120 for which sensors 120 require electric power foroperation; for those embodiments, power source 150 is connected withsensors 120 so as to provide electric power to sensors 120. For someembodiments of the present invention, sensing element 120A may requireelectrical power for operation or transducer 120B may require electricalpower for operation. In alternative embodiments, sensors 120 do notrequire electric power; consequently, connection with electric powersource 150 is unnecessary for such embodiments.

Information processor 130 has information-processing capabilities likethose of a computer. Information processor 130 preferably includesinformation processing devices such as a central processing unit, amicroprocessor, an application-specific integrated circuit, and fieldprogrammable gate arrays. A preferred embodiment of the presentinvention comprises an information processor having a microprocessor.There are numerous microprocessors that are suitable for use inembodiments of the present invention. Microchip Technologies, Inc.produces a number of microprocessors that are suitable for embodimentsof the present invention. Some of the commercially availablemicroprocessors are capable of signal conditioning and analog to digitalconversion of input signals.

Internal communicator 140 is a transmitter capable of transmittinginformation and data received from information processor 130 to areceiver such as external communicator 160 shown in FIG. 1. Preferably,internal communicator 140 is configured so as to be capable ofwirelessly transmitting information to external communicator 160. Forembodiments in which information processor 130 and internal communicator140 are coupled for bi-directional information transfer, it is preferredfor internal communicator 140 to be capable of transmitting informationto a receiver in addition to receiving information from a transmitter.

Reference is now made to FIG. 2 where there is shown a sensor apparatus100, according to one embodiment of the present invention in use in aplasma chamber 170. Sensor apparatus 100 is supported on a workpieceholder 175. Sensor apparatus 100 is exposed to plasma 180 so as to makespatial and/or temporal measurements of a process parameter related toplasma 180 for a plasma process. Plasma chamber 170 is substantially thesame as the types of plasma chambers typically used for processingworkpieces such as semiconductor wafers and flat panel displaysubstrates. Plasma 180 can be generated using typical plasma sourcesused for processing workpieces. It is typical for plasma chamber 170 tohave a robot handler associated with it for loading and unloadingworkpieces, (robot handler not shown in FIG. 2). For preferredembodiments, sensor apparatus 100 is configured so as to be loaded andunloaded to and from process chamber 170 using the robot handler inessentially the same way that workpieces are loaded and unloaded.

Reference is now made to FIG. 3 where there is shown a top view of asensor apparatus 200 according to one embodiment of the presentinvention. Sensor apparatus 200 is configured so as to be capable ofmeasuring parameter data for plasma processing a workpiece. Sensorapparatus 200 includes a base 117, a plurality of sensors 120 such asthe nine sensors shown in FIG. 3, an electronics module 210, andmetallization lines 215 connecting sensors 120 with electronics module210. Sensors 120 and electronics module 210 are supported on or in base117.

Electronics module 210 includes electronic components, preferablycontained on a support structure such as a printed circuit board orcontained in a housing (printed circuit board and housing not shown inFIG. 3). In a preferred embodiment, electronics module 210 contains aninformation processor and additional electronic components that may beneeded for the operation of the information processor. In general,electronics module 210 may contain an information processor, a powersource for the information processor, and an internal communicator. Theelectronic components of electronics module 210 are substantially thesame as those described for the embodiment described in FIG. 1. Morespecifically, electronics module 210 may also contain components fortransmitting and receiving information such as, for example, componentsfor wireless communication. Sensors 120 are connected with theinformation processor so as to allow signals generated by sensors 120 tobe provided as input to the information processor.

Optionally, for some embodiments of the present invention forsemiconductor processing applications, base 117 comprises asemiconductor wafer, preferably a substantially whole semiconductorwafer such as a silicon wafer or such as a gallium arsenide wafer.Similarly, for flatpanel display applications, base 117 may comprise aflatpanel display substrate; for lithography mask applications, base 117may comprise a lithography mask substrate. In preferred embodiments,base 117 is a structure such as a semiconductor wafer, a lithographymask substrate, and a flat panel display substrate. Generally, base 117is configured so as to substantially mimic the workpiece; morepreferably, base 117 comprises the workpiece.

Reference is not made to FIG. 3A where there is shown a top view ofanother embodiment of the present invention. The embodiment shown inFIG. 3A is essentially the same as that shown in FIG. 3 with theexception that the embodiment in FIG. 3A includes metallization lines220 and 225 configured so that the sensors are connected in a crosspointnetwork. More specifically, the transducers for the sensors areconnected as nodes in the crosspoint network. Details of a suitablecrosspoint network are described in commonly owned U.S. Pat. No.6,542,835 and U.S. Pat. No. 6,789,034.

Next, examples of preferred methods for fabricating examples of sensingelements and examples of preferred sensing element configurations forembodiments of the present invention will be presented.

Capacitive Sensing Element

Reference is now made to FIG. 4A. An example configuration of acapacitive sensing element, according to the present invention, is shownin FIG. 4A in a cross-section side view. The capacitive sensing elementincludes a planar conductive electrode 300 of known area. The materialand surface area of electrode 300 are selected to provide compatibilitywith the process conditions to be measured. Conductive electrode 300 mayeither be indirectly exposed to the plasma or, in a preferredembodiment, protected from the plasma by a thin, inert dielectricmaterial 302 as shown in FIG. 4A. An example of a suitable material fordielectric 302 is KAPTON.

The sensing element also includes a second planar conductive electrode304 disposed below electrode 300 and a base 320. Base 320 providessupport for electrode 304; base 320 and electrode 304 are coupled sothat they form a low impedance contact. Preferably, base 320 comprises asemiconductor wafer. For some embodiments of the present invention,electrode 300 has areas in the range 0.1 cm² to 10 cm². Electrode areasbetween 0.1 cm² and 5 cm² are particularly useful. The shape of theelectrode may be circular in order to minimize edge effects or elongatedso as to measure the parameter of interest at a specific circumferenceof the base.

The sensing element also includes a dielectric material 310 of knowncharacteristics located between conductive electrode 300 and conductiveelectrode 304. The thickness and material of dielectric material 310 areselected to minimize the capacitive reactance while providing acceptablevoltage breakdown values. A well-characterized and controlled polymericmaterial such as polyimide, polyester, and polyoly-para-xylylene areexamples of preferred materials for dielectric material 310. For someembodiments of the present invention, the thickness of the dielectricmaterial is in the range of 1 micrometer to 100 micrometers. Morepreferably, the thickness of the dielectric ranges from 10 micrometersto 50 micrometers; this range is of particular value.

Reference is now made to FIG. 4B where there is shown an electricalschematic of a capacitive sensing element 322 such as the sensingelement shown in FIG. 4A. Capacitive sensing element 322 is shownconnected with a transducer 324, also presented as an electricalschematic. Transducer 324 shows an example of a diode transduceraccording to one embodiment of the present invention. FIG. 4B showstransducer 324 having a resistive load, a diode, and a capacitor.Preferred embodiments of the present invention minimize perturbations ofthe plasma produced by the impedance of the sensing element byincorporating a known resistance between the conductive electrode andbase 320; this is a valuable feature for some embodiments of the presentinvention. The magnitude of the resistance of the parallel resistance isselected to provide both minimal perturbation of the plasma and to scalethe voltages generated on the capacitor into values compatible with themeasurement circuit. Resistance values between 10 ohms and 1000 ohmswould be used with sensors of the dimensions given above.

Consistent and reproducible operation of the capacitive sensor isimproved by having a low impedance connection to the base. This lowimpedance connection may be produced by either a direct (ohmic) contactbetween base 320 and conductive electrode 304 formed opposite conductiveelectrode 300 or a capacitive connection formed through the use of avery thin dielectric material. An ohmic contact may be formed throughthe use of a soldered or conductive adhesive connection to the base. Acapacitive connection could be formed by insuring that only a thin (<5micrometers), stable gap exists between the base and a conductive layerformed opposite the electrode.

Numerous specific combinations of electrode areas, shapes, and materialscould be used to provide acceptable measurements. Similarly, there is awide range of dielectric materials, thicknesses, and connection methodswhich could be utilized. In preferred embodiments of present invention,these variables are selected to meet one of more of the following designcriteria: Minimize the perturbation of the plasma state in the proximityof the sensor. Provide a signal amplitude compatible with themeasurement circuitry. Permit fabrication using materials and processeswhich both produce a stable, reproducible structure and are compatiblewith semiconductor device manufacturing cleanliness standards.

Furthermore, it is understood that a capacitive element such as thatdescribed in FIG. 4A and FIG. 4B is by nature sensitive to RF(displacement) currents perpendicular to the surface of the electrodesof a capacitor such as that formed by conductive electrode 300 andconductive electrode 304. Also, it is understood that a capacitiveelement such as that described in FIG. 4A and FIG. 4B is by naturesensitive to RF electric fields perpendicular to the surface of theelectrodes of the capacitor.

Another embodiment of the present invention is a sensor apparatus formeasuring one or more direction dependent electrical properties of aplasma process for processing a workpiece. Reference is now made to FIG.4C where there is shown a sensor apparatus for measuring one or moreproperties of a plasma for two or more directions. FIG. 4C shows aperspective view, primarily, of the top surface of the sensor apparatus.The sensor apparatus comprises a base 342, an information processor 343supported on or in base 342, and a plurality of capacitive sensorssupported on or in base 342 and coupled to information processor 343.The sensors have one or more capacitive sensing elements configured soas to provide an output that represents a plasma process parametermeasurement. Capacitive sensing elements 346A, 346B, and 346C for agroup of three capacitive sensors are oriented so that they each lie ina plane that is substantially perpendicular to the planes for each ofthe other capacitive sensor elements. In addition, capacitive sensingelement 346A is oriented so that it lies in a plane that issubstantially parallel to the surface of base 342. As an option,embodiments of the present invention include two or more groups of threesensors. Other embodiments of the present invention may be arranged sothat there are only two sensors in a group and only two sensing elementsin the group are oriented perpendicular to each other.

In a preferred arrangement for an embodiment of the present invention,configured for measuring a plasma property such as electric fields, thecapacitive sensors or at least the sensing elements are fabricated andmounted on or in the base in various orientations so that electricfields with directions other than perpendicular to the surface of thebase can be measured. Similarly, for embodiments of the presentinvention configured for measuring currents using capacitive sensors,the capacitive sensors or at least the sensing elements are mounted invarious orientations so that currents with directions other thanperpendicular to the surface of the substrate can also be measured.

As an option for some embodiments of the present invention, techniquessuch as those used for microelectromechanical systems, surface mount,and hybrid assembly can be used to fabricate groups of three capacitivesensors in close proximity to each other. Preferably, one of thecapacitive sensors in the group is arranged so that it is substantiallyco-planar to the surface of the base and the capacitive sensors in eachgroup is arranged so that it is perpendicular to the other twocapacitive sensors in the group so that plasma properties such aselectric fields and currents in any direction can be captured andanalyzed through their x, y, and z components.

Inductive Sensing Element

Reference is now made to FIG. 5A where there is shown a cross-sectionside view of an example configuration of an inductive sensing element,according to the present invention. The inductive sensing elementincludes a ring 352 or loop made of a material with a high magneticpermeability. Ring 352 is shown in cross section in FIG. 5A. Thedimensions of ring 352, as represented by enclosed area and crosssection, are selected such that RF currents passing through ring 352induce a magnetic flux within ring 352. In other words, one embodimentof the present invention includes an inductive sensing element having aninduction coil with a core comprising a closed ring of magneticallypermeable material enclosing an area between 0.1 cm² and 10 cm².

Preferred enclosed areas between 0.1 cm² and 5 cm² provide generallyacceptable performance. The ring material typically utilizesferromagnetic elements such as iron and nickel or their alloys. Thesemagnetic materials may be used in either metallic wire or foil form oras oxides in a ferrite composition.

The inductive sensing element also includes an electrically conductivesense coil 354 forming at least one loop enclosing the magnetic flux ofring 352 in a toroidal fashion. Magnetic flux variations induced in theinductive ring induce current flow within sense coil 354. This currentis then monitored as an indicator of the RF current flow through thearea enclosed by ring 352. FIG. 5A also shows base 356 supporting ring352 and a coating of a dielectric 358 substantially covering ring 352.

Reference is now made to FIG. 5B where there is shown an electricalschematic of an inductive sensing element 360, such as that shown inFIG. 5A, and a transducer 370 according to an embodiment of the presentinvention. Transducer 370 comprises a diode transducer. FIG. 5B showsring 352 and sense coil 354. A preferred embodiment of the inductivesensor also includes a resistive load element allowing currents inducedwithin the sense coil to produce a measurable voltage. The enclosed areaof the ring, the number of turns in the sense coils, and the value ofthe load resistance are selected to produce a voltage compatible withthe measuring circuitry. FIG. 5B shows transducer 370 having a resistiveload, a diode, and a capacitor.

An inductive element is by nature sensitive to magnetic RF fields thatare perpendicular to the area of the electrical loops of the coil. Thus,the example depicted in FIG. 5A is sensitive to magnetic RF fields thatare co-planar to the plane of the coil which is parallel to the surfaceof the base. Another embodiment of the present invention comprises asensor apparatus arranged so as to monitor such fields with directionsother than parallel to the surface of the base. More specifically, anembodiment of the present invention includes inductive sensing elementsfabricated and mounted in various orientations on or in the base.

Reference is now made to FIG. 5C where there is shown a sensor apparatusfor measuring one or more properties of a plasma for two or moredirections. FIG. 5C shows a perspective view, primarily, of the topsurface of the sensor apparatus. The sensor apparatus comprises a base365, an information processor 365A supported on or in base 365, and aplurality of inductive sensors supported on or in base 365 and coupledto information processor 365A. The sensors have one or more inductivesensing elements configured so as to provide an output that represents aplasma process parameter measurement. Inductive sensing elements 366A,366B, and 366C for a group of three inductive sensors are oriented sothat they lie in a plane that is substantially perpendicular to theplanes for each of the other inductive sensor elements. In addition,inductive sensing element 366A is oriented so that it lies in a planethat is substantially parallel to the surface of base 365. As an option,preferred embodiments of the present invention include two or moregroups of three sensors. Other embodiments of the present invention maybe arranged so that there are only two sensors in a group and only twosensing elements in the group are oriented perpendicular to each other.

As an option for some embodiments of the present invention, techniquessuch as those used for microelectromechanical systems, surface mount,and hybrid assembly can be used to fabricate groups of three inductivesensors in close proximity to each other. Preferably, one of theinductive sensors in the group is arranged so that it is substantiallyco-planar to the surface of the base. The inductive sensors in eachgroup are arranged so that the sensing element of each sensor isperpendicular to the other two inductive sensor elements in the group sothat plasma properties in any direction can be captured and analyzedthrough their x, y, and z components.

A preferred embodiment of the present invention includes a base, aninformation processor, and inductive sensors comprising planar coils. Abenefit of using planar coils, rather than toroidal coils, is anincreased simplicity of fabrication. A specific application of interestfor some of the embodiments of the present invention involves the use ofplanar coils arranged so that they are substantially co-planar to thesurface of the substrate and configured so as to detect magnetic RFfield components perpendicular to the surface of the substrate. Suchfield components are typically associated with undesirable plasmanon-uniformities and fringing field effects. In another embodiment, theplanar coils are not coplanar to the surface of the base but the planarcoils lie in a plane that is substantially parallel to the surface ofthe base.

There are numerous specific combinations of enclosed areas, shapes, andmaterials which could be used to provide an acceptable measurement.Similarly there is a wide range of conductive coil materials,thicknesses and numbers or turns which could be utilized. In preferredembodiments of present invention, these variables are selected to meetone of more of the following design criteria: Minimize the perturbationof the plasma state in the proximity of the sensor. Provide signalamplitudes compatible with the measurement circuitry. And, permitfabrication using materials and processes which both produce a stable,reproducible structure and are compatible with semiconductor devicemanufacturing cleanliness standards.

Electrostatic Charge Sensing Element

An example configuration of an electrostatic charge sensing element,according to the present invention, includes a material or structurewhich undergoes a measurable change in the presence of an appliedelectrical field such as a voltage gradient. Examples of suitablematerials are semiconductors wherein the applied field can cause themovement of mobile charges within the material leading to changes inapparent resistance. One example of a suitable sensing element comprisesa flexible plate structure wherein the applied field can producedeflection of the flexible plate.

Reference is now made to FIG. 6A where there is shown a cross-sectionside view of an electrostatic charge sensing element according to oneembodiment of the present invention. FIG. 6A also shows a plasma. Thecharge sensing element is placed so as to measure one or more plasmaparameters. The electrostatic charge sensing element includes a flexibleelectrical conductor 372, an electrical conductor 373, a base 374, and adielectric 376. Electrical conductor 373 is fixedly attached to base374. Electrical conductor 372 is suspended substantially oppositeelectrical conductor 374 with a portion of dielectric 376 so as to forma void 378 between electrical conductor 372 and electrical conductor373. In this configuration, an electrical potential applied betweenelectrical conductor 372 and electrical conductor 373 will causeelectrical conductor 372 to deflect with respect to electrical conductor373. The deflection of electric conductor 372 will cause a measurablechange in the capacitance between electrical conductor 372 andelectrical conductor 373. Optionally, electrical conductor 372 maycomprise a metal sheet, a metal plate, or a metal film that issufficiently flexible to produce a deflection in response to an appliedfield. Electrical conductor 373 may comprise a metal sheet, a metalplate, or a metal film.

Reference is now made to FIG. 6B where there is shown an electrostaticcharge sensing element according to another embodiment of the presentinvention, the sensing element includes two electrical contacts 380 and390 spaced apart on a lightly doped semiconductor substrate 400. In thearea between the two electrical contacts, an isolated conductive plate410 is positioned over a dielectric insulating layer 420. A voltage orpotential appearing on conductive plate 410 will induce depletion orinversion in the underlying semiconductor substrate 400, causingmeasurable changes in the apparent resistance of this layer. A varietyof materials and construction methods can be used to produce acceptableresults.

Some embodiments of the present invention do not required the use ofconductive plate 410. A plasma can induce a charge on the surface ofinsulating layer 420 which would also be effective in moderating theconductivity of semiconductor substrate 400.

Next, examples of preferred methods for fabricating examples oftransducers and examples of preferred transducer configurations forembodiments of the present invention will be presented.

Diode Rectification Transducer

One embodiment of the present invention includes a sensor apparatus, asdescribed above, comprising a transducer having a diode rectificationcircuit such as the diode rectification circuit shown for transducer 324in FIG. 4B and such as the diode rectification circuit shown fortransducer 370 in FIG. 5B.

Reference is now made to FIG. 7 where there is shown a diagram of aconfiguration for a transducer 121B coupled between a sensing element120A and an information processor 130. A transducer 121B comprises adiode rectification circuit that includes a semiconducting junctiondiode 500 configured for rectifying an applied AC (RF) voltage or AC(RF) current from sensing element 120A so as to produce a rectifiedvoltage or current. Transducer 121B further includes a simple low passfilter 510. The rectified voltage or current is passed through thesimple low pass filter (e.g. RC) to produce a DC voltage or currentproportional to the applied RF voltage. This type of transducer iscompatible with a variety of sensing elements such as capacitive sensingelements and such as inductive sensing elements which provide a currentoutput proportional to the process parameter being measured. Theappropriate selection of the low pass filtering components can controlboth the apparent impedance of the sensor (e.g. minimize perturbation ofthe local plasma state) and scale the amplitude of the converted signalto be compatible with the measuring circuitry of the informationprocessor. Another embodiment of the present invention uses capacitivecoupling of the diode rectification circuit to the sensing element toeliminate potentially damaging DC current paths or to isolate themeasuring circuitry from excessive voltages.

Power Detection Transducer

Another embodiment of the present invention includes a sensor apparatus,as described above, comprising a transducer having a power detectioncircuit. Reference is now made to FIG. 8 where there is shown a diagramof a configuration for a transducer 1228 coupled between a sensingelement 120A and an information processor 130. Transducer 122B comprisesa power detection circuit that includes a resistive load 520 such as aresistor and a temperature measuring device 530 such as a thermocoupleand such as a thermistor or another type thermometer. Resistive load 520and temperature measuring device 530 are configured so that thetemperature of resistive load 520 is measured by temperature measuringdevice 530.

In one embodiment, resistive load 520 and temperature measuring device530 are arranged such as would occur for temperature measurementsresulting from temperature measuring device 530 physically contactingresistive load 520 for temperature measurement by thermal conduction. Itis to be understood that other configurations are possible; for example,temperature measuring device 530 may be configured for measuringtemperature using thermal radiation. FIG. 8 shows a more preferredembodiment where transducer 122B further includes a thermally conductiveelectrical insulator 525 placed between load 520 and temperaturemeasuring device 530 so that heat flux from load 520 (as indicated bythe arrows in FIG. 8) passes through the insulator to reach temperaturemeasuring device 530.

The power detection circuit couples power captured by sensing element120A into resistive load 520. The power dissipated within resistive load520 results in a temperature increase in resistive load 520. This typeof transducer is used in preferred embodiments of the present inventionfor measuring radio frequency energy and fields because the operation ofthe transducer is relatively frequency independent.

The measurement of the temperature can be done using components whichare electrically isolated from the sensing element. This configurationcan provide a more robust and noise tolerant measurement than transducertypes requiring a direct (or capacitive) electrical connection to thesensing element. A preferred embodiment of the present inventionincludes a resistive load 520 having a resistance between 10 ohms and1,000 ohms a thermal sensor 530 having a resistance between 10,000 ohmsand 5,000,000 ohms.

Optical Transducer

Another embodiment of the present invention includes a sensor apparatus,as described above, comprising a transducer having an opticaltransduction circuit. Reference is now made to FIG. 9 where there isshown a transducer 123B coupled between a sensing element 120A and aninformation processor 130. Transducer 123B comprises an opticaltransduction circuit that includes a light emitting device 540 such as alight emitting diode and a light detecting device 550 such as aphotoresistor or a photodiode. Light emitting device 540 is configuredso that the intensity of the light emitted by light emitting device 540is proportional to the current received by light emitting device 540.Light detecting device 550 is arranged so as to be capable of measuringlight emitted by light emitting device 540 so as to produce a currentproportional to the light produced by light emitting device 540.Transducer 123B is configured so as to allow coupling a current fromsensing element 120A to light emitting device 540. Transducer 123B canbe configured so as to provide electrical isolation from the plasma.

In a more preferred embodiment, transducer 123B further includes anoptically transparent electrical insulator 545 placed between lightemitting device 540 and light detecting device 550 so that opticalemissions (shown as arrows in FIG. 9) from light emitting device 540pass through insulator 545 to reach light detecting device 550. For someembodiments of the present invention, the optical transducer allows theoptical signal to be transmitted to the measurement circuitry via fiberoptic channels. In other words, some embodiments of the presentinvention have insulator 545 comprising optical fibers. Using the fiberoptic channels, signal noise may be reduced.

Another embodiment of the present invention includes a method ofoperating and maintaining a process tool for processing workpieces forwhich the process uses a plasma. The method comprises the steps of:Providing a process tool having a robot for transferring a workpiecefrom a storage container or storage chamber to a workpiece holder.Providing a sensor apparatus configured for measuring one or more plasmaparameters. The sensor apparatus has dimensions and physical propertiesthat are substantially equal to the dimensions and physical propertiesof the workpiece. Using the robot to transfer a workpiece from thestorage container to the holder for performing the process and unloadingthe workpiece from the holder back to the storage container. Using therobot to transfer the sensor apparatus to the holder for performing theprocess. Using the sensor apparatus to measure the at least one plasmacharacteristic during the process, and unloading the sensor apparatusfrom the holder using the robot.

The disclosed method and apparatus enables rapid and cost effectiveassessments of processing conditions within plasma processingenvironments such as those utilized in the manufacture of products suchas integrated circuits and flat panel displays. The ability to directlymonitor the plasma state, in conjunction with appropriate system models,allows the plasma process parameters to be adjusted so as to achieveoptimal process performance.

Use of a sensor apparatus such as those described supra configured fordata acquisition, data storage, and data communications technologyallows accurate, highly resolved measurements to be made onsubstantially unmodified process systems running typical processrecipes. Unlike embodiments of the present invention, the standardtechnology methods of acquiring similar data require modification of theprocess chamber and often require alteration of the process conditions.In addition, the use of a sensor apparatus according to embodiments ofthe present invention that is configured so as to be isolated from aplasma environment by an inert, transparent shield minimizes thepossibility of contaminating the processing system.

One embodiment of the present invention includes a method of deployingmultiple sensing elements responsive to a plasma process parameterwithin a plasma-processing environment. An apparatus according to oneembodiment of the present invention comprises capacitive sensingelements, inductive sensing elements, electrostatic charge sensingelements, or optical emission sensing elements arrayed upon a base thatcan be deployed into the process system utilizing standard roboticloading capabilities of the process system. The measurement of localplasma parameter distributions are used to infer the state of the plasmaand compare the inferred state based on the measurements to a referencestate(s) such as past states of the plasma. Differences between theinferred current state and reference state(s) can be used to adjustplasma parameters so as to optimize the system. This data may then beused for a variety of purposes such as process optimization, processmonitoring, and fault detection/identification.

Embodiments of the present invention may include sensors other thanthose presented above. One embodiment of the present invention includesa sensor apparatus for measuring a plasma process parameter forprocessing a workpiece. The sensor apparatus comprises a base and aninformation processor supported on or in the base. The apparatus furtherincludes an optical sensor supported on or in the base and coupled tothe information processor. The sensor has an optical sensing elementconfigured for measuring an optical property of the plasma related to anelectrical property of the plasma and a transducer coupled to thesensing element, wherein the transducer is selected from the groupconsisting of a diode transducer, a power transducer, and an opticaltransducer.

Another embodiment of the present invention is a sensor apparatus formeasuring one or more plasma process parameters for processing aworkpiece. The sensor apparatus comprises a base, an informationprocessor supported on or in the base, and a plurality of sensorssupported on or in the base. A preferred embodiment includes acapacitive sensor, an inductive sensor, and an electrostatic chargesensor. The capacitive sensor, inductive sensor, and the electrostaticcharge sensor further comprise a transducer selected from the groupconsisting of: (A) a diode rectification transducer comprising asemiconductor junction diode for rectifying an applied radio frequencyvoltage or current and a low pass filter so as to produce a DC voltageor current proportional to the applied RF voltage or current; (B) apower transducer comprising a resistive load having a resistance between1 ohm and 1000000 ohms and a thermistor or a thermocouple disposed so asto measure the temperature of the resistive load; and (C) an opticaltransducer comprising a light emitting device configured so as toprovide light emissions proportional to a signal from the sensingelement and an optical detector configured so as to measure the lightemissions from the light emitting device.

In preferred embodiments of the present invention, the sensor apparatusis configured so as to have a thin form factor. In other words, thesensor apparatus has a thickness that approaches that for the workpiece.The design of the sensor apparatus is selected so as to have the sensorapparatus cause minimum perturbation of the plasma process during themeasurements. For the most ideal design, this means having a thicknessas near as possible to that of the thickness of a silicon wafer or thethickness of a flat panel display substrate or the thickness of alithography mask substrate.

It is to be understood that the construction method and the style usedto integrate and encapsulate the system components may be furthermodified to yield a substantially thinner sensor apparatus, perhaps evenapproximating the thickness of a silicon wafer used for devicefabrication. An embodiment of such a sensor apparatus could beaccomplished with the incorporation of MEMS integrated cavities andoptical radiation sensors combined with hybrid electronic packaging.

In the foregoing specification, the invention has been described withreference to specific embodiments. However, one of ordinary skill in theart appreciates that various modifications and changes can be madewithout departing from the scope of the present invention as set forthin the claims below. Accordingly, the specification and figures are tobe regarded in an illustrative rather than a restrictive sense, and allsuch modifications are intended to be included within the scope ofpresent invention.

Benefits, other advantages, and solutions to problems have beendescribed above with regard to specific embodiments. However, thebenefits, advantages, solutions to problems, and any element(s) that maycause any benefit, advantage, or solution to occur or become morepronounced are not to be construed as a critical, required, or essentialfeature or element of any or all the claims.

As used herein, the terms “comprises,” “comprising,” “includes,”“including,” “has,” “having,” “at least one of,” or any other variationthereof, are intended to cover a non-exclusive inclusion. For example, aprocess, method, article, or apparatus that comprises a list of elementsis not necessarily limited only to those elements but may include otherelements not expressly listed or inherent to such process, method,article, or apparatus. Further, unless expressly stated to the contrary,“or” refers to an inclusive or and not to an exclusive or. For example,a condition A or B is satisfied by any one of the following: A is true(or present) and B is false (or not present), A is false (or notpresent) and B is true (or present), and both A and B are true (orpresent).

Further, unless expressly stated to the contrary, “at least one of” isto be interpreted to mean “one or more.” For example, a process, method,article, or apparatus that comprises one or more of a list of elementsand if one or more of the elements comprises a sub-list of sub-elements,then the sub-elements are to be considered in the same manner as theelements. For example, at least one of A and B is satisfied by any oneof the following: A is true (or present) and B is false (or notpresent), A is false (or not present) and B is true (or present), andboth A and B are true (or present).

Furthermore, a process, method, article, or apparatus that comprises oneor more of a list of elements and if one or more of the elementscomprises a sub-list of sub-elements, then the “at least one” is to beinterpreted to mean “one or more” of the elements and sub-elements wherethe elements and sub-elements are to be considered part of one group ofequal members. For example, at least one of A and B, where A is a listof sub-elements a1, a2, and a3, is satisfied by any one of thefollowing: any sub-element of A is true (or present) and B is false (ornot present), any of or all of the sub-element(s) of A is false (or notpresent) and B is true (or present), and both any sub-element of A and Bare true (or present). For example, at least one of A and B, where A isa list of sub-elements a1, a2, and a3 and B is a list of sub-elementsb1, b2, and b3, is satisfied by any one of the following: anysub-element of A is true (or present) and any sub-element of B is false(or not present), any sub-element of A is false (or not present) and anysub-element of B is true (or present), and both any sub-element of A andany sub-element of B are true (or present).

What is claimed is:
 1. A sensor apparatus for measuring a plasma processparameter for processing a workpiece, the sensor apparatus comprising: abase; an information processor supported on or in the base; anelectrostatic charge sensor supported on or in the base and coupled tothe information processor, the sensor having an electrostatic chargesensing element configured so as to provide an output that represents aplasma process parameter measurement.
 2. The sensor apparatus of claim 1wherein the electrostatic charge sensor includes a transducer coupled tothe sensing element, the transducer being configured so as to receive asignal from the sensing element and converting the signal into a secondsignal for input to the information processor.
 3. The sensor apparatusof claim 1 wherein the base comprises a silicon wafer with a diameter ofbetween 100 mm and 450 mm and the sensor apparatus has a thickness of0.3 mm to 10 mm.
 4. The sensor apparatus of claim 1 wherein the basecomprises a substantially whole semiconductor wafer, a substantiallywhole flat panel display substrate, or a substantially whole lithographymask.
 5. The sensor apparatus of claim 1 wherein the electrostaticcharge sensor includes a transducer coupled to the electrostatic chargesensing element, the transducer being configured so as to receive asignal from the sensing element and convert the signal into a secondsignal for input to the information processor, wherein the transducercomprises a diode rectification circuit.
 6. The sensor apparatus ofclaim 1 wherein the electrostatic charge sensor includes a transducercoupled to the electrostatic charge sensing element, the transducerbeing configured so as to receive a signal from the sensing element andconvert the signal into a second signal for input to the informationprocessor, wherein the transducer comprises a diode rectificationcircuit comprising a semiconductor junction diode for rectifying anapplied radio frequency voltage or current and a low pass filter so asto produce a DC voltage or current proportional to the applied RFvoltage or current.
 7. The sensor apparatus of claim 1 wherein theelectrostatic charge sensor includes a transducer coupled to theelectrostatic charge sensing element, the transducer being configured soas to receive a signal from the sensing element and convert the signalinto a second signal for input to the information processor, wherein thetransducer comprises a power detection circuit that includes: aresistive load having a resistance between 1 ohm and 1000000 ohms and atemperature measuring device disposed so as to measure the temperatureof the resistive load.
 8. The sensor apparatus of claim 1 wherein theelectrostatic charge sensor includes a transducer coupled to theelectrostatic charge sensing element, the transducer being configured soas to receive a signal from the sensing element and convert the signalinto a second signal for input to the information processor, wherein thetransducer comprises a power detection circuit that includes: aresistive load having a resistance between 1 ohm and 1000000 ohms and athermistor or a thermocouple disposed so as to measure the temperatureof the resistive load.
 9. The sensor apparatus of claim 1 wherein theelectrostatic charge sensor includes a transducer coupled to theelectrostatic charge sensing element, the transducer being configured soas to receive a signal from the sensing element and convert the signalinto a second signal for input to the information processor, wherein thetransducer comprises an optical transducer.
 10. The sensor apparatus ofclaim 1 wherein the electrostatic charge sensor includes a transducercoupled to the electrostatic charge sensing element, the transducerbeing configured so as to receive a signal from the sensing element andconvert the signal into a second signal for input to the informationprocessor, wherein the transducer comprises an optical transducercomprising a light emitting device configured so as to provide lightemissions proportional to the signal from the sensing element and anoptical detector configured so as to measure the light emissions fromthe light emitting device.
 11. A sensor apparatus for measuring a plasmaprocess parameter for processing a workpiece, the sensor apparatuscomprising: a base; an information processor supported on or in thebase; and a sensor supported on or in the base, the sensor comprising asensing element configured for measuring an electrical property of aplasma and a transducer coupled to the sensing element, wherein thetransducer is a power transducer having a resistive load for receiving acurrent and a voltage from the sensing element and a thermometerarranged so as to measure changes in temperature of the resistive load,wherein the sensing element is configured to provide an output of acurrent and a voltage that represent a process parameter measurement.12. The sensor apparatus of claim 11, wherein the transducer comprises apower detection circuit that includes: a resistive load having aresistance between 1 ohm and 1000000 ohms and a thermistor or athermocouple disposed so as to measure the temperature of the resistiveload.
 13. A sensor apparatus for measuring a plasma process parameterfor processing a workpiece, the sensor apparatus comprising: a base; aninformation processor supported on or in the base; and a sensorsupported on or in the base, the sensor comprising a sensing elementconfigured for measuring an electrical property of a plasma and atransducer coupled to the sensing element, wherein the transducer is anoptical transducer coupled to the at least one sensing element, thetransducer being configured so as to receive a signal from the sensingelement and convert the signal into a second signal for input to theinformation processor.
 14. The sensor apparatus of claim 13 wherein theoptical transducer comprises a light emitting device configured so as toprovide light emissions proportional to the signal from the sensingelement and an optical detector configured so as to measure the lightemissions from the light emitting device.
 15. The sensor apparatus ofclaim 13 wherein the sensor has an optical sensing element configuredfor measuring an optical property of the plasma related to an electricalproperty of the plasma and the transducer is selected from the groupconsisting of a diode transducer, a power transducer, and an opticaltransducer.